Hi
Yes you need to do both the intake and exhaust cams on this engine. Not sure what the difference in cam size/profile is for the 3.2 over the 3.0, but considerind there is only 5bhp between them its probably nothing usefull.
3.0 manifolds and boring out the head ports to match has allready been mentioned.
The throttle bodies can't be bored out as such but the shaft can be filed down and the large obstructive screw heads replaced with grub screws to open up more area when the butterflies are open and improve the flow capacity (I have performed this modification successfully on my throttle bodies)...message me if you would like me to do yours for you

I assume "all that trunking" you are talking about is the excess of intake pipe in the box its self? :-?
The standard air box is not really restrictive to the engine, and the MAF sensors can be affected by the oil used in filters such as K&N cones etc..so unless you don't mind having to find a new MAF soon I wouldn't really bother spending any money there as it wont give you significant gains.
The exhaust system....hmmm. As yours is a 2.6 I think (but may be wrong) that it allready comes with the improved pressed steel manifold (as opposed to the cast items on the 2.5s and 3.0s. which are more restrictive). Probably best to check that one, but removing the mid silencers is a useful mod to do, reducing back-pressure (an making it louder too

)
Blanking off the EGR can also give small gains in performace.
Spark plugs and leads won't give you any power gains if the ones you allready have are in good condition.
Remaps I know nothing about...probably best start a separate post about that.

Hope that give you some ideas.